Research
Energy balance
There is an inverse correlation between Body Mass Index (BMI) and brown adipose tissue (BAT) activity in adult humans, and BAT activity diminishes with age.
As you age or gain weight, your body's natural ability to burn extra energy via brown fat decreases. This biological shift contributes to the common experience of gaining weight in middle age. While you cannot reverse aging, recognizing this decline helps explain why weight management strategies that worked in your 20s might need adjustment now.
GoodQualifiesHIGH confidence
The consensus from the recent human BAT studies... suggests an inverse correlation between BMI and BAT activity. Saito et al. also provide compelling data that BAT activity diminishes with age.
Why this rating
Based on large-scale analysis (Cypess et al.) and Saito et al. data cited in the commentary.
Source
Brown Fat in Humans: Turning up the Heat on Obesity
Patrick Seale et al. · Diabetes · 2009
DOI 10.2337/db09-0622
narrative_reviewCited 175×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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